--> ABSTRACT: Forward Modeling of High-Frequency, Glacio-Eustatic, Depositional Sequences: An Example from Middle Pennsylvanian Shelf Carbonates of the SW Paradox Basin, Honaker Trail, Utah, by Robert K. Goldhammer, E. J. Oswald, P. A. Dunn; #91003 (1990).
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ABSTRACT: Forward Modeling of High-Frequency, Glacio-Eustatic, Depositional Previous HitSequencesNext Hit: An Example from Middle Pennsylvanian Shelf Carbonates of the SW Paradox Basin, Honaker Trail, Utah

Robert K. Goldhammer, E. J. Oswald, P. A. Dunn

Middle Pennsylvanian (Desmoinesian) shelf carbonates in the southwest Paradox basin display three superimposed orders of stratigraphic cyclicity with a systematic, vertical succession of facies, parasequence, and sequence stacking patterns. Previous HitFifthNext Hit-Previous HitorderNext Hit Previous HitparasequencesNext Hit (34 Previous HitparasequencesNext Hit in 645 ft section; averaging 20 ft thick, 40 k.y. duration) are grouped into Previous HitfourthNext Hit-order Previous HitsequencesNext Hit (averaging 100 ft thick, approximately 400 k.y. duration), which in turn vertically stack to define a third-order accommodation cycle (>= 650 ft thick, 2.4 m.y. duration). Previous HitFifthNext Hit-Previous HitorderNext Hit Previous HitparasequencesNext Hit are comprised of shallowing-upward packages of dominantly subtidal shelf carbonates with sharp parasequence boundaries (exposure or flooding surfaces). Previous HitFifthNext Hit-Previous HitorderNext Hit Previous HitparasequencesNext Hit are packaged into ourth-order Previous HitsequencesNext Hit (type 1) bounded by regionally correlative subaerial exposure surfaces. These type 1 Previous HitsequencesNext Hit contain a downdip, basinally restricted lowstand wedge of evaporites and quartz clastics, a regionally correlative transgressive shaly mudstone (condensed section), and a highstand systems tract composed of thinning-upward, aggradational, Previous HitfifthNext Hit-Previous HitorderNext Hit, Previous HitparasequencesNext Hit. Systematic variation in the thickness of Previous HitfourthNext Hit-order Previous HitsequencesNext Hit (thinning followed by upward thickening), as well as the number of Previous HitfifthNext Hit-Previous HitorderNext Hit Previous HitparasequencesNext Hit/Previous HitsequencesNext Hit (decreasing followed by increasing number), define a third-order accommodation trend, which is also regionally correlative. High-frequency Previous HitparasequencesNext Hit and Previous HitsequencesNext Hit are interpreted as aggradational allocycles generated in response to glacio-eust tic sea level fluctuations driven by Milankovitch climatic forcing. The Previous HitfifthNext Hit-Previous HitorderNext Hit Previous HitparasequencesNext Hit record the earth's orbital eccentricity cycle (mean period of 41 k.y.), and the Previous HitfourthNext Hit-order Previous HitsequencesTop result from the long eccentricity cycle (mean period of 413 k.y.). The parasequence, sequence, and facies stacking patterns have been replicated via computer by superimposing composite, high-frequency glacio-eustasy atop regional subsidence using depth-dependent, facies-keyed sedimentation.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990